The present invention generally relates to a method for forming a pattern on a semiconductor element, and more particularly to a method for forming a fine pattern in a process of semiconductor photoetching.
Ever since high-degree integration of semiconductor elements has become a known technology in manufacturing semiconductor elements, a precise photoetching technology has become a key to getting the high-degree integration.
In general, since a manufacturing process for a semiconductor element includes the repeating steps of coating and forming a plurality of layers or films on a substrate, forming a pattern thereon to make a window, and injecting impurities, it cannot be over-emphasized that how a fine pattern is formed determines reliability of semiconductor element.
FIGS. 1A to 1C illustrate process diagrams of a generally employed conventional photoetching process for forming a pattern.
In FIG. 1A, when a first photomask with a given pattern designed therein is exposed to ultraviolet rays 2, hereafter referred to as ultra-violet 2, photo-sensitive (or photosensitive) materials 4, 5 coated on a semiconductor having a step 3, as shown in FIG. 1B, get differentiated as a photo-sensitive material 4 exposed to the ultra-violet 2 and a photo-sensitive material 5 not exposed to the ultra-violet according to pattern of the first photo mask. However, since the photo-sensitive material (step area) coated on the surface of the step 3 and the other photo-sensitive material (non-step area) coated on the surface of the semiconductor other than the step area, are different in their thicknesses, the non-step area is not completely exposed to the ultra-violet 2 whereby a photo-sensitive material 6 remains unexposed to the ultra-violet 2 when the exposure to the ultra-violet 2 is performed through the first photomask having a given pattern. It can be easily understood that such a problem is caused by irregular thicknesses of the photo-sensitive material due to the existence of the step 3. Because of the problem, an unexposed photo-sensitive material 6 which is in the non-step area still remains as shown in the FIG. 1C, even when the photo-sensitive material 4 exposed to the ultra-violet 2 has been removed by applying a developing solution, so as to block the formation of an accurate pattern. That is, there exists a problem that it is difficult to form a precise and satisfactory pattern on the surface of the semiconductor that has the step.